Using the new improved data provided by LOFAR, we now re-test these interpretations for the low-frequency spectra of hotspots A and D. The model parameters were estimated using a Bayesian 2-level hierarchical analysis, which allows both the measurement errors and the intrinsic scatter in the regression relationship to be correctly accounted for (see [1]} for details). The parameters for the model fits discussed below are presented in Table REF  and the model spectra are shown in Fig. REF . In Table REF , we also give the relative Bayesian evidence for each model, except for the synchrotron-self absorption model (see below).
